The present invention refers to the field of thermal machines. The present invention relates to a heat shield, in particular for gas turbines.
Heat shields for gas turbines are known, for examples, from the publication U.S. Pat. No. 4,573,866 or EP-A1-0 516 322.
In thermal machines such as gas turbines, there are certain contours (for example the annular, stator-side heat shields which surround the rotor blades of the rotor), which are composed of individual segments whose end surfaces abut one another so as to form gaps. Such segmented contours require cooling of the flanks by blowing out a cooling fluid, as a rule cooling air. For this purpose, special cooling holes are provided (88 in FIG. 2 of EP-A1-0 516 322 or C in FIG. 3 of U.S. Pat. No. 4,573,866), through which the cooling fluid is blown out into the gaps.
Under certain operational conditions, however, the gaps between the segments can become practically closed. The openings of the cooling holes emerging into the gaps are then covered by the side walls of the adjacent segments, which leads to a failure of the cooling in this region.
One of the objectives of the invention is, therefore, to create a heat shield which avoids the quoted disadvantages of known heat shields and, in particular, ensures sufficient cooling of the segment edges near the gaps even when the gaps are closed.
The core of the invention consists in providing, in the region of the outlet flow openings of the cooling holes, a widened space which ensures unhindered emergence of the cooling fluid even when the gap is completely closed.
The invention can be effected in a particularly simple manner if, in accordance with a preferred embodiment, the chamber is configured as a recess, which, starting from the thermally loaded side of the heat shield, extends into the gap. The depth of the chamber is then preferably a specified percentage, in particular between 10% and 90%, of the thickness of the heat shield in the region of the gap.
The length of the chamber is, preferably, a specified percentage of the width of the heat shield, in particular between 10% and 80%.